Rechargeable batteries serving as electricity storage devices that store power supplied to a travel motor are installed in vehicles such as an electric vehicle (EV) and a plug-in hybrid vehicle. A known rechargeable battery includes a case, which accommodates, for example, an electrode assembly, and a safety valve, which is arranged on the case and opens when the inner pressure of the case exceeds a release pressure to discharge the gas generated in the case (refer to, for example, patent document 1).